Calendar events created via a CalDAV client with an invitee formats the RRULE incorrectly

Symptoms

After creating an event in a Calendar application connected via CalDAV that has an invitee hosted externally to the server (GMail, Outlook, etc.), the ICS file received by that invitee is formatted incorrectly. This results in the tools to "Import" the event not working, and the ICS file being treated as just an email attachment.

Description

When an event is added to the server with an invitee, the CalDAV service will create an ICS file to send to added users that are hosted externally. However, the generated ICS file from the CalDAV service will incorrectly "escape" the semicolons found in any "RRULE" (Recurrence Rules) line in the file, resulting in the ICS file not being recognized by some external providers.

Events created in RoundCube, or sent to another cPanel server, are handled properly and do not have this issue.

We've opened an internal case for our development team to investigate this further. For reference, the case number is CPANEL-50145. Follow this article to receive an email notification when a solution is published in the product. 

Workaround

Create events using the RoundCube calendar.